Electrical switch



April 1952 K. A. HARMON ET AL ELECTRICAL SWITCH 2 SHEETS-SHEET 1 Filed Feb. 17, 1951 J j WSW Z w me r r t w n i Z m I V /l//////./4,l fi V. 7 vii!!! III B 41M 7 Patented Apr. 1, 1952 UNITED STATES PATENTIIOFFICE 2,591,353 H ELECTRICAL swrron Kenneth A. Harmon, Longmeadow, and Glen A. Guernsey, West Springfield, Mass., assignors to Wico Electric Company, West Springfield, Mass., a corporation of Massachusetts Application February 17, 1951, Serial No. 211,512

6 Claims. 1

This invention relates to an electrical switch adapted to connect an input conductor first to one and then to another of two output conductors and to establish the connection with each output conductor before the connection with the other output conductor is broken.

The invention has for an object an improved switch structure for performing the Work described effectively over long periods of time, even when operated at relatively high speeds of the order of 100 to 150 cycles per second.

The invention has for another object the provision of a switch structure for the purposes described in which the interval of overlap, when the input conductor is connected to both output conductors, is reduced to a minimum and for all practical purposes the engagement of the input conductor with one output conductor is followed almost instantaneously by the disengagement of the input conductor from the other output conductor.

The invention has for another object the provision in an electrical switch of the class described of conveniently roperable means for adjusting the travel of one of its contacts, which reciprocates, relatively to the other two contacts in order to enable intervals of closure of the two circuits to be exactly equal and balanced or to be made unequal to various degrees.

The invention will be disclosed with reference to the one illustrative embodiment shown in the accompanying drawings, in which:

Fig. 1 is a full size exterior elevational view of the switch; 1

Fig. 2 is an enlarged top plan view thereof;

Fig. 3 is an enlarged sectional elevational view taken on the line 3-3 of Fig. 2;

Fig. 4 is an enlarged cross sectional view taken on the line 4-4 of Fig. 2; and

Fig. 5 is a full size end elevational view taken from the right of Fig. 2.

Referring to these drawings and first to Fig. 1 thereof; the switch includes three contacts I, 2, and 3 mounted for relative movement in a direction toward and away from one another. The contact I is an input contact and is adapted to alternately engage the other and output contacts 2 and 3. The arrangement is such that each output contact will be engaged by the input contact before the latter disengages from the other output contact.

Conveniently, these contacts are mounted in the cylindrical chamber 4 of a casing section 5 having a coaxial hub 6 and a clamping ring 1, threaded onto the upper end of the casing. The

peripheral wall of chamber 4 is lined with a thin strip 8 of insulating material. Resting on the bottom wall of the chamber is a washer 9 of insulating material and resting on this washer is the output contact 2, which is in the form of a metallic washer closely fitting the lining l and preferably having its upper surface silver plated. A metallic sleeve I 0 closely fits the lining 8, rests upon the outer marginal portion of output contact 2 and extends upwardly to the top of chamber 4. Resting on top of sleeve I0 is a metallic washer II, on which is superposed a disk I2 of insulating material forming a closure for the upper end of chamber 4. The clamping ring I engages the outer marginal portion of disk I2 and forces it and washer I I downwardly, clamping the washer II tightly against the upper end face of sleeve Ill and forcing the sleeve against the contact 2 and the washer 9 against the bottom wall of the chamber. An upstanding terminal post I3 is riveted to the disk II 'and passes'through disk I2 out of the casing.

Beneath the disk II is a disk I4 of insulating material 1 and beneath disk I4 is a metallic washer I5. An upstanding terminal post I6 has a lower part of reduced diameter passing through disk I 2, through a hole in disk I I and out of contact therewith and through the washers I 4 and I5, being headed' over against the latter, whereby washer I5 is clamped to the cover disk I2 and in electrical contact with the input terminal post I6. A spring I! engages at its upper end with washer I5 and at its lower end with the upper face of the input'contact I, which is preferably cup-shaped, having an annular fiat disk portion functioning as the contact and an upstanding marginal rim encompassing the lower portion of spring IT. The bottom face of contact I is preferably silver plated. The input contact I is larger in diameter than the hole inoutput contact 2 and the spring I! tends to move contact I toward and into engagement with contact 2. The input contact I also has an opening therethrough.

The output contact 3 is an annular disk or washer surrounding a central stud I8, which upstands from a flange I9 on the upper end of a plunger 20, slidably mounted in the hub 6 of easing 4. The stud I8, flange I9 and plunger 20 are integrally united and made of suitable insulating material. The contact 3, preferably having its upper face silver plated, is larger in diameter than the hole in input contact I and smaller in diameter than the hole through contact 2 and washer 9. Contact 3 moves freely in the hole through contact 2 and washer 9, spaced from and out of contact with the wall thereof, and is adapted to engage the inner marginal portion of the input contact I that overlies the hole in contact 2. The contact 3, after engaging input contact I, will lift the latter and carry it out of engagement with output contact 2. There is an instant, when the input contact engages both output contacts, but the described arrangement enables the time of overlap, when both output contacts are connected to the input contact, to

be reduced to a minimum. Except for elasticity of the parts which enables some slight deflections, the overlap interval would be infinitesimal. A spring 2| tends to move the output contact 3 away from contact I. The lower end of this spring extends through the hole in input contact I, encompasses stud I8 and presses against the upper face of contact 3 and the upper end of the spring presses against a metallic disk 22 and encompasses a depending stud 23 thereon. The disk 22 engages the flanged lower end of an insulating plug 24, which fits in the holes in the washers l5, l4 and II. On top of the insulating cover disk I2 is a radial metallic strip 25 (Fig. 4), and fixed to and upstanding from the outer end of this strip is a terminal post 26. The inner end of this strip is connected to the described disk .22

by a rivet 21, which clamps the disk to plug 24- and the latter to washer l and the strip 25 to cover disk 12.

The plunger 29, which carries the output contact 3, is movable by a cam 28, housed in a hollow cylindrical casing section 29, having a rightangularly turned hollow and interiorly threaded hub 30. The hub 6 of the switch casing 5 is ex teriorly threaded and screwed into the hub 30. The arrangement enables the two sections of the casing to be relatively moved in order to adjust the location of the stroke of the reciprocating contact 3 relatively to the contacts I and 2. The casing section 5 is fixed in its various positions of adjustment to the casing section 29 by means of a lock nut 3| which is threaded on hub 6 and forces a lock washer 32 against the end face of hub 30. One end of casing 29 (Fig. 3) has a bearing 33 rotatably supporting one end of a short driving shaft 34 to which cam 28 is suitably fixed, as by the set screw 35 (Fig. 4) threaded into the hub of the cam and bearing against a flattened part of shaft 34. The opposite end of easing section 29 (Fig. 3) is large enough in diameter to enable the passage of cam 23 and has a closure plug 36, which is suitably fixed to the casing section, as by a set screw 31, and carries the other bearing 38 for shaft .34.

The shaft 34 may be operated in any suitable way. In the example shown, shaft 34 is adapted to be interposed in the speedometer drive .of an automobile. One end of shaft 34 has a plug .39 of'square cross section and the other a socket 40 of similar cross section. An interiorly threaded coupling sleeve 41 has an inturned flange encompassing the outer periphery of plug 36 and held axially between the flange on the outer end of the plug and the adjacent end face of casing 29. The opposite end of casing 29 is exteriorly threaded, as at 42, to receive a coupling sleeve similar to 4|. The coupling sleeve of the speedometer cable is disconnected .at the transmission end and the plug 39 inserted in the socket in the speedometer-driving element of the transmission. The coupling sleeve is then applied to hold the casing 29 in.place. Then, the plug end on the speedometer shaft is inserted in socket 40 and the coupling sleeve onthe sheath of the speedometer shaft is screwed onto the threaded end 42 of casing 29.

The several terminal posts I3, l6 and 26 each have a head 43. On each post, and confined between the head and the cover l2, are a spring 44 and a washer 45, which rests on top of the spring and is of a diameter larger than the head. These provisions enable quick connection and disconnection of the terminal posts and the input and output wires 46, 41 and 48 (Fig. 5). These Wires are secured in metal sockets 49, 50 and 5!. These sockets (Figs. 3 and 4) are fixed to and upstand from a disk 52 of insulating material. On the lower face of disk 52 (Figs. 2, 3 and 4) are sector-shaped metal plates 53, 54 and 55, spaced one from another and respectively connected to the posts 49, 59 and 5|, which have portions of small diameter that pass through disk 52 and the respective sector plates and are riveted to the latter. Each sector plate is further held to disk 52 by a rivet 56 (Fig. 2). Each sector plate has a slightly curved keyhole slot 51 therein with the large end adapted to freely pass head 43 but not washer 45 and the small part adapted to freely fit a terminal post. The disk 52 has a curved slot 58, overlying and coextensive with the keyholeslot 56 but of a Width which is uniform throughout its length and which is equal to the diameter of the large end of the keyhole slot. The disk 52, when positioned so that the large ends of the several keyhole slots overlie the several heads 43, is pressed downwardly forcing the sector plates against the washers 45 and increasing the compression of springs 44. Then, when the lower ends of heads 43 lie slightly above the sector plates, the disk 52 is turned to carry the terminal posts into the narrow parts of the keyhole slots after which the disk is released and moved upwardly by the springs 45 until each sector plate is tightly held between the head of its terminal post and the washer 44 thereon.

Desirably, the wires 45, 47 and 48, disk 52 and the switch casing 5 are protected as shown in Fig. 5 by a waterproof enclosure 59.

The operation of the switch will sufficiently appear from the foregoing description.

The switch of this invention finds one advantageous use as a control for an automatic brake holder of an automotive vehicle. For such use, the cam of the switch is driven from the propeller shaft of the vehicle, desirably by being interposed in the speedometer drive thereof, and functions as disclosed in our copending application Serial No. 145,692, filed February 23, 1950, to cause the actuation of a relay at a certain and relatively slow propeller shaft speed. The switch operates continuously, whenever the propeller shaft is driven, and at times at relatively high speeds. For example, the driving shaft of the commercial form of speedometer, commonly used on automotive vehicles, makes 1000 revolutions per mile. If the vehicle is driven at 60 miles per hour, the speedometer shaft will make 1000 revolutions per minute and this will actuate the switch at 6000 cycles per minute or cycles per second. The switch structure described is adapted to operate efliciently and at such high speeds and is calculated to have a long life of useful service. For the particular use described, it is desired to have the intervals, during which each output contact is engaged by the input contact, exactly equal and the construction of the casing in two adjustably-related sections 5 and 29 enables this result to be accomplished quickly and conveniently. For other uses, where the closure intervals of the two circuits need to be unequal, this may also be accomplished by adjustment of the two casing sections to vary the location of the stroke of the contact 3 carried by the reciprocating plunger 20 relatively to the other contacts I and 2.

What is claimed is: I

1. An electrical switch, comprising a first electrical contact having an opening therethrough, a second electrical contact larger than said opening, yieldable means tending to move the second contact toward and into engagement with the first contact, the second contact when engaged with the first contact partially covering said opening, a third electrical contact smaller than said opening and mounted to move in a direction toward and away from the second contact through the opening in spaced relation with the wall of such opening, said third contact adapted periodically to engage the second contact and move it away from the first contact, and means for reciprocating the third contact in said direction.

2. An electrical switch, comprising a first electrical contact having an opening therethrough, a second electrical contact larger than said opening, yieldable means tending to move the second contact toward and into engagement with the first contact, the second contact when engaged with the first contact partially covering said opening, a third electrical contact smaller than said opening and mounted to move in a direction toward and away from the second contact through the opening in spaced relation with the wall of such opening, said third contact adapted periodically to engage the second contact and move it away from the first contact, means for reciprocating the third contact in said direction with a stroke of predetermined length, and adjustable means for varying the location of such stroke relatively to said first and second contacts.

3. An electrical switch, comprising, a first electrical contact stationarily mounted and having an opening therethrough, second and third electrical contacts mounted in coaxial relation with the stationary contact for movement in the direction of the common axis of said contacts, the second contact being larger than the opening in the first contact and overlapping said opening, a spring for moving the second contact toward and into engagement with the first contact, the third contact being smaller than said opening and movable freely through such opening in spaced relation with its wall to engage the second contact and move it away from and out of engagement with the first contact, and means for reciprocating the third contact in the direction of said axis, whereby the second contact may engage first with the first contact then momentarily with both the first and third contacts and then only with the third contact.

4. An electrical switch, comprising, a casing, a first electrical contact stationarily mounted therein and having an opening therethrough, a second electrical contact larger than said opening and mounted in said casing coaxially of the first contact, a spring tending to move the second contact toward and into engagement with the first contact, a plunger mounted in the casing for reciprocating movement in the direction of said axis, a third electrical contact carried by said plunger smaller than said opening, a driving shaft mounted in said casing with its axis at right angles to the axis of the plunger, a multi-lobed cam fixed to said shaft and engaging said plunger to reciprocate the same with a stroke sufficient to carry the third contact through said opening into engagement with the second contact and to lift the second contact from the first contact.

5. An electrical switch as claimed in claim 4 in which the casing is constructed in two sections one of which carries the cam and driving shaft and the other of which carries the contacts, and means for moving one such section relatively to the other in the direction of the axis of said plunger, whereby to vary the location of the stroke of the latter and the third contact relatively to the first and second contacts.

6. An electrical switch, comprising, a casing having opposed end walls and a peripheral wall interconnecting the end walls and forming therewith a cylindrical chamber, one end wall being a removable cover, a first electrical contact in the form of a washer located coaxially of the chamber and adjacent the other end wall and insulated therefrom, a metallic sleeve lining the peripheral wall and insulated therefrom and having one end face engaged with the outer marginal portion of the first contact, a series of terminal disks fixed to and insulated from the cover and from each other, said disks being located coaxially of the chamber and being of progressively decreasing diameter with the largest farthest from the second-named end wall and having its outer marginal portion engaged by the other end face of said sleeve, a second electrical contact also in the form of a washer having outer and inner diameters respectively greater and less than the diameter of the hole in the first contact, said second contact located coaxially of the first contact, a spring acting between the second contact and the intermediate terminal disk tending to engage the second contact with the first, a third electrical contact located coaxially of the other two contacts and having a diameter less than that of the hole in the first contact and greater than that of the hole in the second contact, a plunger mounted in the second-named end wall for reciprocation in the direction of the common axis of the contacts and carrying the third contact, a multi-lobed cam engaging one end of the plunger, and a spring less in diameter than the hole in the third contact located between the smallest terminal disk and the third contact and passing through the hole in the second contact for holding said plunger against the cam, said springs serving as electrical connections between the second and third contacts and their respective terminaldisks.

KENNETH A. HARMON. GLEN A. GUERNSEY.

REFERENCES CITED UNITED STATES PATENTS Name Date Koppleman Jan. '7, 1941 Number 

